Donald Trump has told Central and Eastern European leaders that “America will be your strongest ally and your steadfast partner” in their attempts to reduce dependence on Russian energy supplies, encouraging the nations to take advantage of fast-growing supplies of accessible U.S. natural gas.

“We stand ready, willing and able to stand by you for your energy needs,” said the U.S. president, speaking in Warsaw at a summit devoted to the Three Seas Initiative, a project aiming to expand and modernise energy infrastructure among 12 European countries located between the Baltic, Adriatic, and Black Seas.

Promoting U.S. exports of liquefied natural gas, the first shipment of which arrived in Poland last month, Mr. Trump said: “We are here to launch a new future for open, fair, and affordable energy markets which will bring prosperity to all of our citizens.”

“You are united by the hope your citizens will flourish, your commerce will prosper, and your countries will absolutely thrive,” the president told leaders. “I know that is what is going to happen because I know the people.

Noting that the region holds “special significance” for him, Mr. Trump — whose wife Melania is from Slovenia — praised the “inspiring” history of nations participating in the Initiative, most of which had to fight to end Communist rule.

President Trump speaks at the Three Seas conference in Warsaw Thursday / AP IMAGES

“You have overcome years of oppression. It’s been 20 years since your brave citizens defeated Communism,” said the president, asserting that “the Three Seas will rebuild and transform the entire region.

“Together, our nation and yours can bring greater peace prosperity and safety to all of our people.”

Ahead of a meeting with Mr. Trump Thursday morning, Polish President Andrzej Duda said the visit would strengthen their place in the EU.

“This is the second foreign visit by President Trump and it starts in Poland. This shows we are a country that matters and it strengthens our position in the European Union,” he said, speaking on public radio.

During his meeting with Mr. Duda, the president announced: “[The U.S. has] never been closer to Poland than we are right now.”